Wood-bending apparatus



July 10, 1923.

F. H. BANCROFT WOOD BENDING APPARATUS Filed April 2'? 1922 4 Sheets-Sheet 1 V I nvgnfor Evin/1H. flaficrofi 71117 altoriiqgr WOOD BENDING APPARATUS Filed Avril 2'7. 1922 4 Sheets-Sheet 2 1% l iutnlifiauarofl 1 WV LMW Q 11f attorwqgl July 10, 1923.

F. H. BANCROFT WOOD BENDING APPARATUS 4 Sheets-Sheet 5 /I///. l I 1 Filed April 27 1922 i W 1 m a S H Ill/l III/l 1 Inventor NN WRN 1 912111? )1 Bancroft Ma W in; fitter)? July 10, 1923. 1,461,471

F. H. BANCROFT WOOD BENDING APPARATUS Filed April 27, 1922 4 Sheets-Sheet 4 I71 men for Franizflfiauavft 7a: a flaring Patented July 10, 1923.

UNITED STATES g 1,461,471 PATENT OFFICE.

mm H. BANCROI'T, OF GARDNER, HASSACHUSETTB, ASBIGII'OB T0 P. DERBY & (30., Hill, 01 WORCESTER, MASSACHUSETTS, A CORPORATION 01 MASSACHUSETTS.

WOOD-BINDING APPARATUS.

Application filed April 27, 1922. Serial Io. 558,980.

To all whom it may cmwcm:

Be it known that I, FRANK H. BANOBOFI, a citizen of the United States of America, and resident of Gardner, in the count of Worcester and State of Massachusetts, ave invented new and useful Improvements in Wood-Bending Apparatus, of which the following is a specification.

This invention relates to apparatus for bending wood of small or moderate thickness for fashioning the curved or irregu larly bent parts used in the construction of furniture of various kinds such as chairs, tables, dressers and the like, also the felloes of wheels, etc. The advisability of applying pressure to the ends of wood to be bent prior to and during the bending operation has long been known but hit-or-miss methods heretofore employed for applying such pressure have been inefiicient and wasteful to a high degree, resulting in breakage of from 30 to 50% even when the best of stock is used.

One method in common use is to provide eccentrically mounted members for supporting the stock, each of said members having a fixed abutment for the end of the stock such as a shoulder. As the stock is bent the supporting members swing on their pivots and in an arbitrary and inflexible manner maintain or increase the end pressure upon the stock depending upon the design and mounting of the members and the accuracy with which the stock is cut to size. Another method provides manually operable pressure applying means necessitating the stopping of the a paratus from time to time during the hen ing operation to manually adjust the pressure upon the ends of the stock. This last method requires considerable skill and experience upon the part of the operator and is time consuming and laborious. Even with the greatest care and skill breakage averaging 30% will occur when good stock is used, the percentage mounting fast when poorer stock is used. Lack of experiment to determine the practical effects of end ressure at the various stages of the bending operation as well as apparatus not designed and constructed to avoid excessive and uneven pressure appears to be responsible for poor results heretofore obtained. By reason of the high percentage of breakage the manufacturer must glue and otherwise doctor up at least a portion of the broken stock to prevent operating at a loss Hence a considerable amount of im erfect furniture finds its Way upon the mar et.

Objects of the invention are to reduce the breakage of stock, to speed up the bending process, to eliminate the necessity of highlyskilled operatives, to permit the use of poorer stock, to simplify and facilitate the use of apparatus of this kind, and in eneral to overcome the defects of previous Wood bending devices.

The invention comprises a wood bending machine provided with means for automatically maintaining a uniform end pressure upon the ends of the stock during the bending operation. It further comprises maintaining a balanced pressure upon ends of the stock during the bending operation. This uniform and balanced pressure is pro vided by interconnected fluid pressure means, preferably in the form of hydraulic rams mounted upon the bending heads and operating plungers, means being provided in the connection to the rams for relieving excessive pressure, such as a relief valve. The plungers are constructed and arranged to abut against slides having a limited range of movement upon the ends of the stra upon which the stock tobe bent is place The means for retaining the slides on the strap permit a connection across the form after the stock is bent to permit its removal while still in the form from the machine for the purpose of drying. Adequate means for properly supporting the bending heads, which are heavily unbalanced by the rams thereon, are provided in all positions thereof to take the strain from the other parts, particularly from the master strap which forms the flexible connection between the heads.

For the purpose of illustrating this invention one concrete embodiment thereof is shown in the accompanying drawings, in

Fig. 1 is a front elevation showing the parts in position to bend a piece of wood;

Fig. 2 is a similar view of the upper part of the machine at one stage in the bending operation, several of the parts being shown in section;

Fig. 3 is a view similar to Fig. 2 showing the position of the parts at the end of the bending operation;

Fig. 4 is a plan view of the machine with the parts in the position shown in Fig. 1;

Fig. 5 is a section on the line 5-5 of Fi 1;

Fig. 6 is a sectiori on the line 6-6 of Fig. 1;

Fig. 7 is an elevational view of an attachment to the bending heads;

Fig. 8 is a plan of the left end of F g. 7;

Fig. 9 is a detail sectional view showmg the connection of one end of the master strap to a bending head and the wood supporting strap thereon;

Fig. 10 is an end elevation of a portlon of the strap; and

Fig. 11 is a plan view of the parts shown in Fig. 10.

In the bending machine shown for the purpose of illustration only those parts which extend above the normal position of the floor are disclosed. these parts being shown in elevation in Fig. 1. The machine comprises a stationary frame securely mounted upon a foundation below the floor line which in general is indicated by the broken off portions of the machine shown in Fig. 1. The parts shown rest upon the lower casting 12 from which four posts 13 extend upwardly. these posts having shoulders adjacent the top thereof upon which rest the top casting 14, securely held thereon by nuts 15 upon the top of the posts. This top casting comprises two side plates connected in any suitable manner as by an I-section 16 integral therewith. Guided for vertical reciprocal movement in the frame is a table 17 provided with guide openings formed by plates 18 through which posts 13 extend. This table is reciprocated longitudinally of the posts by any suitable means, such as hydraulic rams (not shown) disposed beneath the level of the floor, and moving the table by means of rams 19. To insure even movement of the table 17 racks 20 are provided upon the under side thereof extending vertically downward in substantially parallel relation with rods 19. Upon lower casting 12 a shaft 21 is mounted in bearings 22 for rotative movement, the opposite ends of this shaft having keyed thereto pinions 23 in mesh with rack bars 20.

Upon the upper face of table 17 are brackets 24 to which are pivoted links 25 connected at their free ends by means of pivots 26 to bending heads 27. Slidable upon the upper face of bending heads 27 are plungers 28 having outwardly projecting flanges 29 slidable in guide grooves 30 in heads 27 These plungers are connected by rods 31 to pistons 32 in hydraulic cylinders 33 fast upon the outer ends of the heads. The heads are connected by a flexible strip of sheet metal 34 known as the master strap, the ends of which are bent upon themselves as indicated at 35 (Fig. 9)

to fit in grooves 36 rovided therefor in the bending heads 2 these ends bein clam ed in position by a suitably shape meta key 37 driven in the opening in the bent over end in the master stra after it has been inserted in groove 36. l his master stra serves as the support for the material to e bent and links the bending heads together as they move upward during the bending operation.

Upon this master strap 34 is placed a strap 39 upon which the block of wood a to be bent is directly placed. The opposite ends of strapI 39 are provided with slides 40 generallyT -shaped in cross section as indicated in ig. 10, the vertical portions of the slides forming inner and outer abutment members and the connecting portion being provided with longitudinal slots 41. These slides are retained upon the strap and limited as to movement thereon by blocks 42 having projecting portions 43 which pass through slots 41 in the slides and are anchored to the strap itself by any suitable means such as screws 44. Upon the top of block 42 is an integral extension or projection 45 provided with an opening 46, the purpose of which will be later set forth.

Attached to the under face of the central I-beam portion of the top casting 14 as by bolts 47 is a bracket 48, the lower portion of which is generally rectangular in front elevation and hollow and rovided with longitudinally disposed pro ecting flanges 49 on the sides thereof. Bracket 48 is intended to support as indicated the forms b about which the wood is to be bent. These forms are ordinarily constructed of wood having a groove in the top of proper size to receive the lower portion of the supporting bracket 48, the groove being preferably undercut to receive flanges 49 so that the form will not fall away from its support. Adjustably mounted directly beneath bracket 48 is a block 50 one end of which has a screw threaded opening 51 through which a threaded shaft 52 passes, said shaft being suitably mounted for rotation in lower casting 12. The opposite end of block 50 has an opening 53 through which a guide shaft or post 54 extends and along which block 50 slides when shaft 52 is rotated to raise or lower the block in adjusting its position. Mounted for vertical movement within a suitable recess or depression in the upper face of block 50 is a slide 55 operated and held in adjusted position by any suitable mechanism as by a threaded shaft 56 received in a threaded opening in block'50 and actuated by a hand wheel 57.

Shaft 54 is clamped in adjusted position upon a casting 58, fast upon the lower easting 12 of the frame by the provision of a clam ing member 59.. The casting 58 is teen orced by vertical parallelly disposed integral ribs in which a plurality of openings 61 are provided, disposed in staggered relation. These openings are adapted to loosely receive a bolt 62 which serves as astop for table 17.

By the provision of hydraulic rams 33 upon the outer ends of bending heads 27 the latter are heavily overbalanced in an outward direction. To prevent undue strain upon the master stra 34 WlllCh serves as the sole connection etween the two heads members 65 shown separately in Fig. 7 are attached to the under side of the bending heads as by bolts 66 and are shaped to extend beneath the bearings for pivots 26 and straight outwardly beneath the master stra as shown in Figs. 1, 2 and 3. These mem ers act as levers which fulcrum near their outer ends upon the wood whlch is to be bent and the form 5 so that the bendin heads are caused to swlng about the fu crum point so determined, and relieve the master strap of undue bending strain.

Members 65 may be provided with an extension 67 for bracing and partially supporting the hydraulic rams Members 65 and 67 are preferably constructed of bar steel as indicated in the plan view in Fig. 8. When a longer master strap 34 is used than that shown in the illustrations, it will be necessary to lengthen members 65 in order to cause them to function in the desired manner. While an interfitting or telescoping arrangement might be used to lengthen these members I prefer to use separate extensions consisting of a tongue 70 having pins 71 extending therethrough. This tongue is adapted to be received between the bifurcated ends 72 of member 65, the pins 71 fitting in suitable slots 73 as indicated. The extension is preferably also provided with bifurcated ends 72 also provided with slots similarly disposed so that another extension may be added thereto if necessary.

To further support the heavy hydraulic rams when the bending heads are in normal position as shown in Fig. 1, I provide supports or rests 75 having tubular portions 76 telescoping over the reduced ends of shafts 77 fast n on a lower casting 12 by the provision 0 nuts 78. Rest 75 is retained in adjusted position by the provision of clamping or set screw 79.

The hydraulic control means to the various rams for operating the mechanism are shown in Fig. 1. The inlet or su ply pipe 80 has a branch 81 leading to ya ve 82 by which fluid under pressure is admitted to pipe 83 which extends upwardly to the top of the frame leads into two branches 84 and 85 (Fig. 4), the former leading by means of pipes 86, 87, 88 to the ram on the left hand bending head. Branch 85 leased leads through pipes 89, 90, 91 to the hydraulic ram on the right hand bending head. The fluid under pressure may be re from thcse rams by operating valve 92 (Fig. 1) which permits fluid to pass through branch 93 into outlet or exhaust pipe 94. Pipe 83 is provided with a by-pass 95 containing the relief valve 96 whereby the pressure in the system containing the rams of the bending heads may be main tained uniform, the relief valve permitting the fluid to flow around valve 92 into branch 93 and thence into exhaust pipe 94.

The fluid is admitted to the rams for operating table 17 (not shown) by a branch 97 from inlet pipe 80 to inlet control valve 98 which admits fluid under pressure into pipe 99 leading to the rains. This pressure may be relieved to permit the table 17 to drop to its lower position by opening valve 100, whence the fluid under pressure passes through branch 101 into exhaust pipe 9 1.

The method of operation is as follows: With the proper size of master strap 34 in place and the bending heads in the position shown in Fig. 1, the operator places a strap 39 of the proper size with a piece of stock a thereon which is to be bent. upon the master strap, the slides 40 thereon being adjacent the plungers 28 of the bending heads. Since the strap 39 is ordinarily of steel and the wood has been steamed and is wot, a strip of copper or brass c is preferably placcd between the stock a and the strap to prevent discoloration of the stock by the action of the acid in the latter on the steel strap. A form b of the proper size and shape is now placed upon the bracket: 48. and the operator turns hand wheel 57 to force slide 55 upwardly to clamp the straps and stock securely against the under side of the form. The parts are now in the position shown in Fig. 1. The operator now opens valye 82 and permits fluid under pressure to enter the cylinders of rams 33 forcing the pistons inwardly whereby plungers 28 operated thereby contact slides 40 upon opposite ends of strap 39 and compress the ends of the stock a. After a sufficient amount of fluid has been admitted valve 82 is closed. The valve 98 is then opened to admit fluid to the rams which move tablel'i'. As the table 17 rises. the bending heads 27 are lifted. first compressing the central portion of the stock against the form, and then wrapping it about the form as the heads move upwardly. The pressure upon the ends of the stock remains balanced by the provision of the interconnection of the ipes, and uniform by reason of the relief valve 96. \Vhen the bending heads reach the position shown in Fig. 2, a reverse curve at d frequently occurs. This curve is ironed out as the bending IUU heads reach the upper limit of their movement shown in Fig. 3. The straps are so proportioned that when this position is reached the slides 40 thereon have been forced back to the limit of their movement as the stock has lengthened in the bending operation. With the parts in the position shown in Fi 3 the operator places a block e upon woo en form b, then hooks a bent rod f of the proper shape across block e and into the openings 46 in extensions 45 of blocks 42 of straps 39. An additional wedging block 9 may be inserted if necessary.

The bent wood is now securely made fast to the form b. The operator then opens valve 92 to release the pressure in the rams on the bending heads, then he opens valve 100 releasing the pressure in the rams operatin table 17 which returns to the position fixe by stop 62. The hand wheel 57 is then 0 erated to lower slide and release the c amping pressure upon the bottom of-the stock. The form I) with the bent wood d thereon together with the strap and the rod f are removed as a unit, and left to dry in that position until the bend becomes set.

The end pressure which has been found to give very satisfactory results upon s ock of an inch to an inch and a quarter in thickness with six inch ram is 350 lbs. to the square inch, the relief valve 96 being set to that pressure. With heavier stock a greater end pressure may be necessary. By t e provision of a balanced and uniform end pressure the wastage of stock'has been reduced from 20 to 50 per cent by ordinary methods to about 5 per cent with this machine. Not only has a great saving in stock been produced, but the machine has been successfully used with poorer stock than is ordinarily used for bending The critical angle in which breakage ordinarily occurs is from 5 to 40 angular displacement of the bending heads from the straight line position. By maintaining a uniform and balanced end pressure and by moving the table 17 upward with a relativel slow but steady movement, poor stock wit knots in the critical area have been bent without breakage.

I claim:

1. In a machine for bending wood about a form, means for clamping a portion of the wood to be bent against the form and means for automatically maintaining a uniform pressure upon the ends of the wood during the bending process.

2. In a machine for bending wood about a form, means for clam ing a portion of the wood to be bent against the form and means for automaticall maintaining a balanced pressure upon t e ends of the wood durin the bending process.

3. n a machine for bending wood about a form, means for clamping a portion of the wood to be bent against the form and means for automatically maintaining a uniform and balanced pressure upon the ends of the wood during the bending process.

4. A wood bending machine having means for initially subjecting a piece of wood to be bent to end pressure of a predetermined amount and means for automatically maintaining said pressure uniform during the bending process.

5. A wood bending machine having fluid premure means for applying pressure to the ends of the wood being bent and means for maintaining the pressure uniform throughout the bending operation.

6. A wood bending machine having fluid pressure means at each end of the wood being bent to apply pressure thereto, said means being interconnected whereby the pressure upon the opposite ends of the wood is balanced throughout the bending process.

7. A wood bending machine having fluid pressure means at each end of the wood being bent to apply pressure thereto, said means being interconnected whereby the pressure upon the opposite ends of the wood is balanced, and means for maintaining the pressure uniform throughout the bending operation.

8. A wood bending machine having hydraulic rams constructed and arranged to apply pressure at the ends of wood to bebent, said rams being interconnected to provide a balanced pressure, and a relief valve for the connection between the rams for maintaining the pressure uniform throughout the bending operation.

9. A wood bending machine having a pair of bending heads, means connecting said heads and adapted to support wood to be bent, means for moving said heads to bend the wood, and fluid pressure means mounted on said headsand constructed and arranged to maintain a balanced pressure on the ends of the wood during heads.

10. A wood bending machine having a pair of bending heads, means connecting said heads and adapted to support wood to be bent, means for moving said heads to bend the wood. and fluid pressure means mounted on said heads and constructed and arranged to maintain a uniform and balanced pressure on the ends of the wood during the movement of said heads.

11.- A wood bending machine having a support for a form, pair of bending heads adjacent thereto, means connecting said heads and adapted to support wood to be bent, means for clamping the wood against a form on said support, means for moving said heads to bend the wood about said form, and slidable means mounted on said heads and constructed and arranged. to a ply a uniform pressure to the ends of tl ie wood during the movement of said heads.

the movement of said 12. A wood bending machine having a pair of bending heads, a strap supporting the wood to be bent mounted upon said heads, means slidably mounted on the ends of said strap to contact the ends of the wood, and means including plungers on said heads for maintaining a uniform pressure upon said slidable means during the movement of said heads to perform the bending op eration.

13. A wood bending machine having a pair of bendin heads, means supporting a strap upon sai heads, the wood to be bent being placed upon said strap, slides on th ends of said strap for contacting the ends of the wood, and fluid pressure means 011 said heads for maintainin uniform pressure upon said slides during t e bending operation.

14. A wood bedding machine having a pair of bending heads, means supporting a strap upon said heads, the wood to be bent being placed upon said strap, slides on the ends of said strap for contacting the ends of the wood, plungers on said heads for moving said slides, and means maintaining a balanced pressure on said plungers.

15. A wood bending machine having a pair of bendin heads, means supporting a strap upon sal heads, the wood to be bent being p aced upon said strap, slides on the ends of said strap for contacting the ends of the wood, plungers on said heads for moving said slides, and hydraulic rams on said heads constructed and arranged to maintain a balanced pressure on said plungers during the bending o ration.

16. A ben ing machine com rising a frame, a table reciprocable in sai frame, a pair of bending heads separately pivoted to said table in outwardly overbalanced relation thereto, flexible work supporting means connecting said heads, and means fast upon said heads and extending beneath said flexible means to control the position of the heads through engagement with the flexible means.

17. A bending machine comprising a frame, a table reciprocable in said frame, a pair of bending heads separately pivoted to said table in unbalanced relation thereto, flexible work supporting means co'nnecting said heads, and members fast .upon said heads and engaging said flexible means to variably control the position of theheads.

18. A bending machine comp 'sing a frame, a table vertically reciprocabl on said frame, a pair of bending heads separately connected to said table by means of links, a flexible member connecting said heads, fluid pressure rams on said heads, and adjustable means for limiting the downward movement of said table when saidheads and flexible member are in substantially straight line position.

19. A bending machine comprising a frame, a table verticall reciprocable on said frame, a pair of bending heads separately connected to said table by means of links, a flexible member connecting said heads, and adjustable sto means on said frame adapted to be dispose in the path of movement of said table to limit the downward movement thereof when said heads and flexible member are in substantially straight line position whereb the machine may be adjusted for use with flexible members of different lengths.

20. A bending machine comprising a frame, a table verticall reciprocable on said frame, a pair of bending heads separately connected to said table by means of links, a flexible memberconnecting said heads, fluid pressure rams on said heads, and means for supporting said rams when said heads are in a. position of rest.

21. A bending machine comprising a frame, a table vertically reciprocable on said frame, a pair of bending heads separately connected to said table by means of links, a flexible member connecting said heads, fluid pressure rams on said heads, and ad- ]ustable means on said frame for supportin said rams when said heads are at the limit of their downward movement.

22. A bending machine comprising a frame, a table vertically reciprocable on said frame, a pair of ben ing heads separately connected to said table by means of links, a flexible member connecting said heads, fluid pressure rams on said heads, stop means for limiting the downward movement of said table, and adjustable rests for supporting said rams when in retracted position.

23. In a wood bending machine, a strap for supporting wood to be bent, said strap having slides comprising spaced abutments and means mounted between said abutments and fastened to said strap for retaining said slides on said strap and for limiting the movement thereof.

24. In a wood bendin machine, a strap for supporting wood to bent, said strap havin slides comprising spaced abutments and b ocks attached to said strap and extending between said abutments for retaining said slides on said strap and for limiting the movement thereof.

25. In a wood bendin machine, a strap for supporting wood to Ire bent, said strap having slides comprising spaced abutments integrall connected, said connection having slots, an means fast to said strap through said slots for retaining said slides on said strap and for limiting the range of movement thereof.

26. In a wood bendin machine, a strap for supporting wood toie bent, said strap having slides comprisin spaced abutments integrally connected, connection having slots, and blocks fast to said strap through said slot for retaining said slides on said strap and for limiting the range of movement thereof.

27. In a Wood bending machine, an elongate strap for supporting wood to be bent, said strap having a movable abutment memher at each end, each member comprising spaced abutments and a longtitudinally slotted integral portion connecting said abutments, and a block having prqections extendin through said slots and fast to said strap or retaining said member on the strap and for limitin the range of its movement.

28. In a wood bending machine, an elongate strap for bending wood about a form, said strap havingslides at the ends thereof comprising spaced abutments, and means fastened to said strap and extending between said abutments for retaining said slides on said strap and for limiting the movement thereof, said means being constructedand arranged for permitting a connection therebetween across the form after the wood is bent, whereby the bent wood together with i said strap having slides at the ends thereof 1 comprising spaced abutmcnts, and blocks fastened to said strap and extending between said abutments for retaining said slides on said strap and for limiting the movement thereof, and means on said blocks for permitting a connection therebetween across the form after the wood is bent, whereby the bent wood together with the form and the strap may be removed as a unit for drying the wood.

. Signed by me at Gardner, Massachusetts, this 24th day of April, 1922.

FRANK H. BAN CROFT.

Certificate Correction. It is hereby certified that the domicile of the essignee in Letters Patent No.

.1 461,471, Lgranted July 10, 1923, upon the application of Frank H. Bancroft, of rdner, essachusetts for an improvement in Wood-Bendix: Apparatus, was

erroneously given as 'Worcester -Massechusetta, "whereas aai domicile should have been given as Gardner, Massachusetts, as shown the record of assignments in this oflice; and that the said Letters Patent should read with this correction therein that the same may conform to the record of the case in the Patent Ofioe.

' Signed end eeeled this 14th day of August, A..D., 1923.

[m] KARL FENNUG,

'Acting Commissioner of Patents. 

